Border render in mesh
This is a bit unlikely because your mention of "vertex group", but a problem most similar to "render border" is when active camera's Clipping distance is too limiting for the scene's size. For example, the following scene is using default camera:



Lower-right object is of regular size, and intersects the camera's Start/near clipping distance. While upper-left object is 10 times larger and bumps into the camera's End/far clipping distance.

If this is the case, relevant settings you need to adjust are in Properties window > Object Data tab > Lens group for the camera object.